1. Field of the Invention
The present invention relates to a preservative solution employed in an ink-jet recording apparatus.
2. Description of the Related Art
In an ink-jet recording method, recording is performed by generating fine droplets of ink according to various ink ejection methods, causing them to fly, and allowing the ink to adhere to a recording material such as paper. In such a case, the ink droplets are generated by an ink ejection method such as: an electrostatic attraction method by means of the application of high voltage; a drop-on-demand method in which mechanical vibrations or displacements are applied to ink by use of a piezoelectric element; or a thermal method which utilizes the pressure generated when the ink is heated to generate a bubble. When using an ink-jet recording method, less noise is generated, and both high-speed printing and multi-color printing are possible.
When an ink-jet recording apparatus is shipped or is held in long-term storage, a preservative solution is filled into the ink passage of the ink-jet head, irrespective of the type of ink ejection method used. In this manner, ink can be smoothly introduced into the ink-jet head without causing bubbles to be caught in the ink at the time of ink introduction after shipping or long-term storage.
A water-based ink containing water as the main solvent has been widely employed as the ink employed in ink-jet recording apparatuses.
In an ink-jet recording apparatus, rubber members are employed in an ink passage comprising an ink tank and an ink-jet head. These rubber members include: a cap which covers the nozzles of the ink-jet head; a wiper which cleans nozzle surfaces of the ink-jet head; a packing seal which is placed at the joint portion between components; a tube which supplies ink from the ink tank to the ink-jet head if the ink tank is provided separately from the ink-jet head; and the like.
However, when a preservative solution or ink comes in contact with the rubber members, additives contained in the rubber members are dissolved in the preservative solution or the ink. The dissolved additives then precipitate out as insoluble materials, thereby causing problems such as clogging of nozzles of the ink-jet head. With regard to the abovementioned problems for ink, a coloring agent exerts a chelating effect to trap components dissolved from the rubber members, whereby the precipitation of the insoluble materials is prevented to some extent. However, since a preservative solution does not contain a coloring agent, the problem of precipitation of the insoluble materials from the rubber members is more prevalent for the preservative solution.
In order to prevent clogging of the nozzles of an ink-jet head, various proposals have been made, such as: using a maintenance solution containing a chelating agent such as a polyaminocarboxylic acid; and cleaning an ink-jet head with a cleaning solution containing a chelating agent such as ethylenediaminetetraacetic acid.
However, even when the conventional maintenance solution or the conventional cleaning solution is employed, it is difficult to effectively prevent the occurrence of precipitation caused by contact of the preservative solution with the rubber members.